Terephthalic acid (TPA) is a highly valuable commercial chemical with a large production capacity. For example, TPA serves a raw material in the production of polyester. Production processes for TPA typically include the liquid phase oxidation of p-xylene with air. The catalyst used is typically a combination of cobalt, manganese, and bromide ions dissolved in acetic acid. Due to the large production capacity of TPA, any improvements to the process with regards to efficiency are very important from an economic point of view. Furthermore, current commercial processes produce harmful impurities. For example, 4-carboxybenzaldehyde (4-CBA) is an impurity that acts as a chain termination agent in subsequent polymerization processes. As a result, the crude TPA produced must undergo a cumbersome and expensive purification process. Therefore, the reduction of 4-CBA levels in the TPA production process is highly significant. In addition, the catalysts used often include highly corrosive acetic acid and bromide ion promoters. These corrosive promoters inconveniently require the use of expensive titanium steel equipment.
Thus, there is a need for a simple and efficient process that can yield valuable TPA with improved catalytic activity, minimal production of harmful impurities, and minimal use of corrosive catalyst promoters.